its all about anticpation.
You are afterall the last line of defense. As far as handling, punching, or reflexes, that mainly comes with experience and practice.
Reading the game and covering your angles is something that you have to be very coordinated.
See how many steps you are from one post to the other, as time passes you will know where the goal is without counting.
See how many steps you are from the penalty spot, and the endline of the goal area.
Remember that if you go a little forward, you cover more angle for shots but you loose more ground.
Look at it this way. If you draw a half circle from one post to the other. You can do that in x amount of steps. If you enlarge this circle to the point that its from the right of the goalies box to hte left, then you will need more leg work. You can cover an angle being more forward. But if there is a switch of play, you will be slower to switch, and nevermind dipping shots that although may be slower in comparison still are fast for you not to catch them.
As far as jumping goes. It is getting a feel for the ground. It looks tough, especially when Khan does them, but most of the time, you will be acting on instcnt which is also going to preapre you for the drop usually. You don't necessary need to much height like Khan, you can adda quick step and punch it out rather than hold it in your hands.
We could be witnessing the greatest left foot ever